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FHB Block 4 > L3- Hypothalamic-Pituitary Relationship > Flashcards

L3- Hypothalamic-Pituitary Relationship Flashcards

1
Q

What is the main role of the hypothalamus?

A

The hypothalamus integrates signals from other brain regions to stimulate the release of hypothalamic-releasing hormones.

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2
Q

What is the organization of the hypothalamus?

A

The hypothalamus is divided into discrete hypothalamic nuclei.

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3
Q

What is the median eminence?

A

ME- the median eminence, is one of the hypothalamic nuclei.

It makes up the floor of the hypothalamus, and serves as a convergence point for axons.

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4
Q

Sleep is regulated by which hypothalamic nuclei?

A

The Suprachiasmatic nucleus (SCN)

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5
Q

Feeding behavior/satiety is regulated by which hypothalamic nuclei?

A

Arcuate nucleus (ARC)

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6
Q

Thirst is regulated by which hypothalamic nucleus?

A

Paraventricular Nucleus- PVN

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7
Q

Reproduction is regulated by which hypothalamic nuclei?

A

Preoptic nucleus (POA)

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8
Q

Circadian rhythms are regulated by which hypothalamic nuclei?

A

Suprachiasmatic nuclei (SCN)

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9
Q

Mood/emotion/stress are regulated by which hypothalamic nuclei?

A

Paraventricular nucleus and arcuate nucleus

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10
Q

Body temperature is regulated by which hypothalamic nucleus?

A

Preoptic nucleus (POA)

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11
Q

Blood pressure is regulated by which hypothalamic nucleus?

A

Paraventricular nucleus (PVN)

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12
Q

GnRH and GnIH are released from what hypothalamic nuclei?

A

Scattered, but the majority are from the POA (preoptic)

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13
Q

CRH (corticotropin releasing hormone) is released from which hypothalamic nuclei?

A

Paraventricular Nucleus - PVN

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14
Q

TRH peptide is released from which hypothalamic nucleus?

A

PVN

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15
Q

GHRH is released from which hypothalamic nuclei?

A

Arcuate nucleus

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16
Q

Somatostatin (GHRH inhibitor) is released from which hypothalamic nuclei?

A

Periventricular (PeVN)

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17
Q

Dopamine is released from which hypothalamic nuclei?

A

Arcuate Nucleus

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18
Q

How big is TRH? What are its second messengers?

A

TRH is 3 amino acids (tiny) –> shorter half-life

TRH uses IP3/DAG/PKC as second messengers

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19
Q

How big is GnRH? What are its second messengers?

A

GnRH is 10 amino acids –> medium sized

GnRH uses IP3/DAG/PKC as second messengers

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20
Q

How big is CRH? What are its second messengers?

A

CRH is 41 amino acids –> large

CRH uses cAMP as second messengers

21
Q

How big is GHRH? What are the second messengers?

A

GHRH is 44 amino acids–> large

GHRH uses cAMP as a second messenger

22
Q

How big is GHIH (somatostatin)? What are the second messengers?

A

GHIH is 14 amino acids –> medium

GHIH/somatostatin uses cAMP as a second messenger

23
Q

Describe the prevalence of GnRH producing cell bodies?

A

Relatively few

24
Q

Where do the very long axons of the GnRH cell bodies extend to?

A

THe median eminence

25
Q

Describe the timing of the GnRH release

A

GnRH is released in a pulsatile manner.

26
Q

What is Kallman Syndrome?

A

Rare genetic disease in which GnRH neurons fail to enter the CNS. It is characterized by reproductive failure and anosmia (inability to smell)

This is a heritable as either an X-linked or autosomal problem

27
Q

What is the hypophysial portal system?

A

A vascular connection between the hypothalamus and the pituitary gland

28
Q

Explain the importance of hypothalamic and pituitary pulsatility.

A

The rate of GnRH pulsatility directly affects the release of LH and FSH release from the anterior pituitary

Fast pulse –> more LH
Slow pulse –> more FSH

29
Q

Through what subunit are the different anterior pituitary hormones differentially regulated by GnRH release?

A

the beta-subunit.

TSH, FSH, LH and hCG all share a common alpha subunit, and the beta subunits are regulated by their respective hypothalamic-releasing hormones

30
Q

What is the difference between the tuberoinfundibular system and the neurohypophysial tract?

A

Tuberoinfundibular system: comprises all neurons that send axonal projections to the median eminence. Hormones target the anterior pituitary through the capillary system (endocrine).

Neurohypophysial tract: comprises neurons whose axons terminate in the posterior pituitary (no NOT have a portal system)

31
Q

What is another name for pituitary?

A

Hypophysis

32
Q

What are the three anatomical divisions of the anterior pituitary?

A 
Pars distalis (90%)
Pars tuberalis
Pars intermedia
33
Q

What are the two anatomical divisions of the posterior pituitary?

A

Pars nervosa

Infundibulum (stalk)

34
Q

Differentiate the type of tissue in the anterior vs posterior pitutiary

A

Anterior: glandular tissue- cords of epithelial cells
Posterior: neural tissue (terminal axons and glial cells- part of neurohypophysial tract)

35
Q

What is another name for posterior pituitary?

A

Neurohypophysis

36
Q

Magnocellular neurons are found in which hypothalamic nuclei?

A

The Paraventricular nucleus (PVN)

37
Q

Axons from magnocellular neurons terminate where?

A

Neurohypophysis (posterior pituitary)

38
Q

What are the major hormones released from the posterior pituitary?

A

Arginine vasopressin (AVP/ADH) and oxytocin

39
Q

How do hormones from the posterior pituitary enter systemic circulation?

A

The neurohypophysis has it’s own capillary bed. The terminal axons of the magnocellular neurons release AVP and OXY directly into the blood stream

Axons terminate near fenestrated capillaries

40
Q

What are Herring bodies?

A

Herring bodies are dilations of unmyelinated axons near the terminals of magnocellular axons in the posterior pituitary.

This is the site of hormone release

41
Q

Name 3 types of anterior pituitary cell types. Differentiate them by color following staining.

A

Acidophils (light stain), Basophils (dark stain) and Chromophobes (clear)

42
Q

What hormones are released from acidophils in the anterior pituitary?

A

Somatotrophs- GH

Lactotrophs- Prolactin

43
Q

What hormones are released from basophils in the anterior pituitary?

A

Corticotrophs- ACTH
Gonadotrophs- LH/FSH
Thyrotrophs- TSH

44
Q

What is released from the chromophobes of the anterior pituitary?

A

Paracrine actions- health maintenance of the other pituitary cells

45
Q

Discuss the relative position of the median eminence and the blood brain barrier

A

The median eminence lies outside the blood brain barrier - signals that regulate the ME can come from the periphery as it doesn’t have to cross the blood brain barrier

46
Q

Discuss the distribution of anterior pituitary hormone cell distributions

A

Cells cluster in regions- (regional distribution)

47
Q

Axons release hormones from the hypophysial portal system to the anterior pituitary where?

A

At the median eminence.

They travel throughout the anterior pituitary via the hypophysial portal system

48
Q

How does the release of most pituitary hormones vary throughout the day?

A

Most pituitary hormones have a circadian rhythm - this is important and must be considered when taking blood samples to evaluate endocrine disease.

FHB Block 4 (15 decks)

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